A method of applying limitation to torque of a motor, in which inverter temperature is detected by a temperature sensor, a temperature variation amount is calculated, correction of the inverter temperature is performed when the temperature variation amount is higher than a threshold value, and also, smoothing processing is performed to the inverter temperature after correction, and when the temperature to which the smoothing processing is performed is higher than an upper limit temperature, a load limitation rate is set is known (Patent Document 1).